Symptoms

SP2013 version of the K2 Form Viewer App Part does not have customisation options that were available in the old WebPart for SharePoint 2010.
Those are the options depicted there:
http://help.k2.com/onlinehelp/k2smartforms/userguide/current/default.htm_Using_the_K2_Forms_Viewer_Web_Part.html
 

Diagnoses

Custom ToolPart Area in not available in K2 Form Viewer AppPart. There is an existing feature request to investigate possibility of adding this in the future versions of our product (TFS 613468).
 

Resolution

SP2013 version of the K2 Form Viewer App Part does not have customisation options which were available in the old WebPart for SharePoint 2010. There is an existing feature request to add those.